Noninvasive diagnostic tests of the function of internal organs are of great value to clinical diagnoses. With respect to pancreatic function, the 72-hr fecal fat test is the "gold standard". However, due to the problematic compliance when used as an outpatient test, the high cost when hospitalization is required, and the time required to obtain results, this test is not normally in the battery of tests used in clinical practice. We are developing a breath test for fat malabsorption which is based on the detection of 13-CO2 in the breath after the ingestion of a 13C-labeled fatty substrate. This concept was based on previous studies using 14-CO2, but this new test involves the detection of the nonradioactive isotope of carbon - Carbon- 13. During Phase I, we shall develop a breath test similar to that for fat malabsorption, but which is more specific for pancreatic dysfunction. This test is based on the differential excretion of 13-CO2 from either a labeled triglyceride substrate, or a labeled fatty acid substrate. Thus, the test measures pancreatic function by assessing the amount of pancreatic lipase present in the gut. The feasibility of this approach will be determined by documenting the response to the test using healthy adult volunteers as well as patients with clinically diagnosed pancreatic dysfunction. Although the sample size will be small during Phase I, the results should indicate its overall feasibility and allow us to determine whether or not the concept should be further developed into a more comprehensive series of clinical trials during Phase II.